ITS DIGESTIVE POWER. 33 



erroneously led to adopt the most extreme views. The difficulty 

 of forming a decided judgment without a special investigation will 

 be best seen from the following historical sketch of the facts which 

 have been accumulated in reference to this subject. Wright,* 

 whose views are based on a large number of experiments, is one 

 of the strongest supporters of the digestive powers of the saliva; 

 and If formerly entirely coincided in this view; but all experi- 

 ments and results bearing on this point must only be adopted with 

 the greatest caution, for there is no analytical inquiry in which, 

 under apparently precisely similar relations, the same experiment 

 so often yields different results, and in which quantitative deter- 

 minations so invariably present a want of uniformity. Thus, the 

 quantities of starch converted into sugar in contemporaneous expe- 

 riments with the same saliva, and at perfectly equal temperatures, 

 are often extremely different. Even when there is only a very' 

 small quantity of starch in relation to the saliva, we almost always 

 find that the whole of it has not undergone conversion into sugar, 

 as was observed by Jacubowitsch ; it is only after a very consider- 

 able time, seldom before from 16 to 24 hours have elapsed, that 

 we find the whole of the starch changed ; and then the starch is 

 not merely converted into sugar, but this latter substance has 

 already undergone further changes, and has given rise to the 

 formation of lactic acid a change which often commences while 

 very large quantities of starch still remain unchanged. We must 

 further bear in mind that many other animal substances under 

 certain conditions possess a similar power of converting starch 

 into sugar. Liebig long ago observed that gelatin and albuminous 

 and gelatigenous tissues, when they had been lying in a state of 

 moisture, and exposed for some time to the atmosphere, possessed 

 the property of effecting this change. MagendieJ subsequently 

 convinced himself that infusions of cerebral tissue, of heart, liver, 

 lungs, and spleen, possessed to a certain degree the power of con- 

 verting starch into dextrin and sugar ; he likewise found that the 

 serum of blood at 40 possessed this property, and that boiled 

 starch was converted into sugar even in the circulating blood of 

 the living animal. Hence Bernard^ merely repeated the experi- 

 ments of Liebig and Magendie, when he exposed well-prepared 

 and cleaned buccal mucous membrane to the air, and subsequently 



* Op. cit. 



t Schmidt's Jahrbb. Bd. 37, S. 121-123, Bd. 39, S. 155 ff. 

 $ Compt. rend. T. 23, pp. 189-192. 

 Arch. gn. de Med. 4 S<r. T. 13, p. 10. 

 VOL. II. D 



